At least for the first 12 feet of run away from the house the pipe should be non-perforated. It does not matter whether the pipe is surrounded by gravel or sand or dirt.

For the entire run the pipe should slope downhill away from the house.

Whatever is at the far end must accept and dissipate the water so it can never back up to the house. If water sits in the pipe then your system is not properly constructed.

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__________________The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.

Check at Lowes or Home Depot for a storm water containment system, works on the same premise as a dry well. And as far as the underside of your deck being a mud pit when it rains, there is a product called underdeck basically it's gutter system installed under your deck.

I have been in the landscaping trade now going on 13the years and have seen underground downspout drains installed with both drain tile and pvc pipe.
I choose to use pvc pipe.
I , in my area of Wisconsin, don't use pop up emitters though as they hold water and will freeze possibly cracking your pipe.
You can get around this by drilling a small hole in the 90° bend at the base and digging a small vertical french drain under your weep hole.
I prefer to daylight all my drains if possible, but when I can't I drill a small weep hole.
A straight daylit pipe also has less chance to plug from leaves and debris.

This is an old thread but just thought I'd say thanks to everyone. I got this completed over the summer and it's working like a charm so far. Have two gutters that goto two 4" PVC pipes.. then they goto a Y to one 4" PVC (one 4" pvc is plenty actually as it's a townhouse) and that 4" pvc dumps just past my fence.

Unfortunately I couldn't easily daylight the drain (while keeping the pitch) so it sits underground and I used a pop up drain. I have the 4" PVC goto a T that sits like this: -| that's about 8" underground. I dug a small trench, filled it with gravel and wrapped it with landscape fabric, and set the bottom part of the T on it. The other end of the T goes to a pop up emitter. The trench below helps the water drain out of the pipe (although on heavy downpours it can stay full for a little while, no big deal I guess). Thanks everyone for the help!